Impeller



July 17, 1962 L. A. SCHMITT, JR

IMPELLER Filed April 8, 1960 2 Sheets-Sheet 1 INVENTOR. LAWRENCE A. SCHMlTT, Jr. gUAJ pm/flu ATTORNEYS July 17, 1962 A. SCHMITT, JR 3,044,750

IMPELLER Filed April 8, 1960 2 Sheets-Sheet 2 ElE- 4:

INVENTOR/ LAWRENCE A. SCMITT, Jr.

ATTORNEYS 3,044,750 WELLER Lawrence A. Schmitt, J12, Fort Wayne, Ind., asslgnor to Sher Dispersion Equipment (10., Inc., Fort Wayne, Ind. Filed Apr. 8, 1960, Ser. No. 21,019 12 Claims. (Cl. 259-134) This invention relates generally to apparatus for agitating a liquid mixture in a container and more particularly to an impeller for such apparatus, especially suited for dispersing solids or liquids in liquid materials, such as for example, the mixing of paint.

While many forms of impellers have been provided for mixing and dispersion purposes, to the best of the present applicants knowledge, all such prior impellers when rotated at a high speed produce a deep vortex in the liquid material. A vortex is a partial vacuum and thus air is continually flowing into the vortex in an effort to satisfy the partial vacuum and is entrained in the material being mixed or dispersed. Such entrained air causes a substantial increase in the volume of the material being mixed or dispersed which, in the particular case of paint, requires a substantial delay before the paint can be canned, in order to permit the entrained air to leave the material by rising to the surface.

It is accordingly an object of my invention to provide an improved mixing and dispersing impeller which substantially reduces the vortex provided by prior impellers known to the present applicant, thus substantially eliminating entrained air in the liquid mixed or dispersed thereby so that paint or other materials mixed or dispersed are ready for immediate canning without the usual delay.

Another object of my invention is to providean improved impeller particularly suited for dispersing solid materials in liquids which provides improved shearing of the solid particles.

Further objects and advantages of my invention will become apparent by reference to the following description and the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

My invention, in its broader aspects, provides an impeller for agitating a liquid mixture in a container comprising a disc arranged for concentric attachment to a rotatable driving shaft. A plurality of elongated impelling vanes project generally at right angles to the plane of the disc and are evenly spaced around the disc adjacent its outer periphery. Each of the vanes hasat least one opening formed therethrough for relieving the vortex which tends to be formed in the mixture due to rotation of the impeller therein; as the impeller is rotated, the liquid is forced through the openings in the impeller vanes toward the center of the disc thus substantially reducing the vortex and also providing an additional swirling flow of the mat rial, thereby enhancing the agitating or dispersing action. In the preferred embodiment of my invention, the openings through the impeller vanes taper inwardly toward the outer surfaces of the vanes thereby forming sharp edges at the outer surfaces which assist in shearing solids in the material and the leading edge of each vane has a sharp hook-shaped portion formed thereon which further assists in shearing solid particles of the material.

in the drawing, FIG. 1 is a side elevational view, partly in section, illustrating a mixing and dispersing machine incorporating my improved impeller;

FIG. 2 is a plan view of the impeller of FIG. 1; FIG. 3 is a fragmentary side elevational view of the impeller of FIG. 2; and

3,044,750 Patented July 17, 1962 FIG. 4 is a cross-sectional view along the line 4-4 of FIG. 3.

Referring now to FIG. 1, there is shown a mixing and dispersing machine, generally identified at 10 which comprises a horizontal base element 12 and a vertical supporting element 14; element 14 may be a hydraulic cylinder having piston 16 therein for selectively elevating and lowering bridge member 18 in order to insert or remove the impeller, to be hereinafter described, from a container of liquid to be mixed or dispersed.

In the illustrated embodiment, the bridge member 18 is shown as being rigidly attached to piston element 16 with driving motor 20 depending from bridge member 13 on one side of supporting element 14 and with vertically downwardly extending rotatable drive shaft 22 depending from bridge member 18 on the other side of supporting element 14, as shown. Motor shaft 24 and drive shaft 22 extend upwardly through bridge member 18, being journalled in suitable bearings (not shown) and respectively having sheaves 26 and 28 attached thereto with a suitable drive belt 39 interconnecting sheaves 26 and 23 whereby motor 20 drives rotatable drive shaft 22.

.The impeller 32 of my invention is attached to the lower end of rotatable drive shaft 22 and in FIG. 1, piston 16 is shown in its lower position so that drive shaft 22- extends into container 34 of material to be mixed with impeller 32 being spaced from the bottom thereof, as shown.

Referring now to the additional figures of the drawing, impeller 32 is formed of a disc 36 of relatively thin metal, such as steel, with a central opening 38 formed therein for concentrically mounting impeller 32 on drive shaft 22. Disc 36 has a plurality of elongated impelling vanes 40 integrally formed on its outer periphery and alternately extending upwardly and downwardly generally at right angles with respect to the plane of disc 36, as best seen in FIG. 3.

As best seen in FIG. 2, impeller 32 is rotated in the direction shown by the arrow 42 and the leading edge 44 tion a of impelling vanes 40 should be between approximately 10 andapproximately 30 and in a specific embodiment of my invention, the angle a. is approximately 15. I have employed impellers in accordance with my invention in which the height of vanes 49 has a.

ratio to the diameter of circle 46 between approximately one-to-fifteen and approximately one-to-twenty five.

' In accordance with my invention, andin order toeliminate the vortex inherently formed in fluids due to high speed rotation of prior impellers, I provide in each vane '49 two horizontally spaced holes 5t) extending through the vane. If will be seen by reference toFlG. 2 that when impeller 36 is rotated at a high speed, such as 2,000 r.p.m., the liquid in the container 34 exerts a very high force against the outer surfaces of the vanes 4i),

this force in turn causing the liquid to be forced through openings 5d toward the center'of disc 36. Referring now 1 additionally to H6. 1, conventional impellers of the type here under consideration, without openings 59 through I, the vanes provide a swirling action in the liquid being mixed or dispersed which resembles a Figure 3 in crosssection, as shown in dashed lines 52 and 54. The liquid which is forced through the holes fill in vanes '40 toward the center of disc 36 tends to fill and thus substantially reduce the vortex normally caused in the liquid being mixed, and further provides an additional Figure 8 swirling action, as shown by the dashed lines 56 and 58; use of my impeller provides only a shallow vortex, as shown by dashed line 59, rather than the deep vortex provided by prior impellers. in addition to reducing the vortex and in turn eliminating entrained air in the liquid being mixed, the flow of liquid through the holes 50 has a shearing effect tending to shear solid particles in the liquid being dispersed, thus appreciably lessening dispersion time.

As best seen in FIG. 4, each of the holes 50 is countersunk with its wall tapered inwardly toward the outer surface 60, thereby defining a sharp edge 62 with the outer surface, this sharp edge further assisting in the shearing of solid particles in the mixture. This taper of holes 50 is shown as having an angle c with respect to the axis of the holes 50 in FIG. 4. I have found that the angle of this taper, for best results, should be between 40 and 50, and preferably approximately 45.

As best seen in FIG. 3, the leading edge 64 of the vane 60, i.e., in the direction of rotation 42, is tapered rearwardly at an angle shown as b, with respect to a line perpendicular to the plane of disc 36. I have found that the angle [1 should preferably be between approximately and 40, and preferably approximately In addition, I have provided a semi-circular cut-out portion 66 in the leading edge 64 of each vane 40 which has its wall tapered inwardly toward outer surface 60 of the vane 40, as shown in FIG. 4 at an angle shown as d which preferably is the same as the angle 0. In the preferred embodiment of my invention, holes 50 have a diameter at the outer surface 6% of vanes 40 which is approximately half the height of vanes 40 above the respective surface of disc 36. The semi-circular cutout portion 66 in the leading edges 64 of vanes 40 are a segment of a circle having approximately the same diameter as the holes 50 at the outer surface 60 of the vanes 40. It will be seen that the sharp edge 68 defined by the tapered wall of the semi-circular cut-out portion 66 with the outer surface 66 of vanes 40 provides additional shearing action, and more particularly, the semi-circular portions 66 in essence define a sharp hook portion 68 which further facilitates the shearing action and is particularly effective in dispersing pigments in paint and cold cutting resins.

An impeller constructed in accordance with my invention for dispersing pigments in paint and intended to be operated at rotational speeds up to 2400 r.p.m. Was formed of stainless steel 72 inch thick with circle 46 having a diameter of eight inches, and the extreme outside diameter to the circle defined by the trailing edges 70 of vanes 40 being nine inches. This impeller had a total of sixteen vanes 40 each projecting /2 inch above the respective surface of disc 36 and each 1% inches long at its base or junction with base 36. The angle a defined by vanes 40 with cord 48 was 14, and the angle b formed by the leading edges 64 of vanes 40 was 25. Each vane 46 had two holes 50 each having a inch diameter at the outer surface 60, the angle of taper 0 being 45. Semi-circular cut-out portions 66 in leading edges 64 of vanes 40, if extended to form a complete circle, would have a diameter of inch at the outer surface 60 and their angle of taper d was the same as the angle 0. I have found that fifty gallons of paint which has been mixed with this impeller rotating at 2400 r.p.m. in order to disperse the pigment therein can be canned immediately with no subsequent loss of volume due to release of entrained air in the paint. With prior impellers operating at comparable speeds, the vortex formed was so deep and wide that it was possible to look directly down the drive shaft 22 and to see the radially inner portions of the impeller, whereas with the improved impeller of my invention, the depth of the vortex is reduced by at least 50%.

4 The number of vanes 40 for any given impeller will depend upon the diameter. Thus, impellers having the following maximum outside diameters (the diameter de fined by the trailing edges 70 of the blades 40) may have the number of vanes indicated:

The proper rotational speed of the impeller will depend upon diameter, however, I believe that for optimum dis- .persing action, the rim speed should be on the order of 5,000 feet per minute. Thus, I have operated a four-inch diameter impeller at 4500 rpm, an eight inch diameter impeller at 2400 rpm. and a twelve and one-half inch diameter impeller at 1600 rpm.

It will now be readily apparent that I have provided an improved liquid mixing and dispersing impeller which, by elimination of the vortex and thus entrained air in the fluid being mixed or dispersed, permits immediate canning of the material mixed or dispersed, and further, the impeller of my invention provides improved shearing action, thus reducing the time required for dispersing pigments in paint, cold cutting of resins, etc.

While I have illustrated and described a specific embodiment of my invention, further modifications and improvements will occur to those skilled in the art and I desire therefore in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What is claimed is:

1. An impeller for agitating a liquid mixture in a container at high speed comprising a disc having means for concentrically attaching the same to a rotatable shaft for rotation in a predetermined direction, and a plurality of elongated impelling vanes projecting generally at right angles to the plane of said disc and evenly spaced around said disc adjacent its outer periphery, each of said vanes having its leading edge coincident with a circle concentric with said shaft and being inclined outwardly and rearwardly therefrom, each of said vanes having means for directing liquid inwardly toward the center of said disc for relieving the vortex which tends to be formed in said mixture due to rotation of said impeller therein.

2. An impeller for agitating a liquid mixture in a container at high speed comprising a disc having means for concentrically attaching the same to a rotatable shaft for rotation in a predetermined direction, and a plurality of elongated impelling vanes projecting generally at right angles to .the plane of said disc and evenly spaced around said disc adjacent its outer periphery, each of said vanes having its leading edge coincident with a circle concentric with said shaft and being inclined outwardly and rearwardly therefrom, each of said vanes having at least one opening formed therethrough for relieving the vortex which tends to be formed in said mixture due to rotation of said impeller therein.

3. An impeller for agitating a liquid mixture in a container at high speed comprising a disc having means for concentrically attaching the same to a rotatable shaft for rotation in a predetermined direction, and a plurality of elongated impelling vanes alternately projecting upwardly and downwardly from said disc and evenly spaced around said disc adjacent its outer periphery, each of said vanes having its leading edge coincident with a circle concentric with said shaft and being inclined outwardly and rearwardly therefrom, each of said vanes having at least one opening formed therethrough for relieving the vortex which tends to be formed in said mixture due to rotation of said impeller therein.

4. The combination of claim 3 wherein said vanes are integrally formed from said disc.

5. The combination of claim 2 wherein each of said openings is in the form of a countersunk hole with its wall tapering inwardly toward the radially outer surface of the respective vane and defining a sharp edge with said outer surface thereby to shear solid particles in said mixture.

6. The combination of claim 2 wherein the leading edge of each vane has a sharp hook-shaped portion formed thereon thereby to shear solid particles in said mixture.

7. The combination of claim 2 wherein the leading edge of each vane tapers outwardly and rearwardly and has a generally semi-circular cut-out portion formed therein with the wall thereof tapering inwardly toward the outer surface of the vane and defining a sharp edge therewith thereby forming a sharp hook-shaped portion for shearing solid particles in said mixture.

8. The combination of claim 7 wherein the taper of the leading edge of each of said vanes is between approximately 20 and approximately 40 from the vertical.

9. The combination of claim 2 wherein the ratio of the height of said vanes to the diameter of said disc is between approximately one-to-fifteen and approximately one-totwenty-five.

10. The combination of claim 2 wherein said vanes are integrally formed from said disc at its outer periphery with each vane having the base of its leading edge coincident with a circle concentric with the center of said disc and being inclined outwardly from a cord of said circle equal in length to the length of the vane by an angle between approximately 10 and approximately 30.

11. An impeller for agitating a liquid mixture in a container at high speed comprising a relatively thin disc having means for concentrically attaching the same to a rotatable shaft for rotation in a predetermined direction, and a plurality of evenly spaced elongated impelling vanes integrally formed from said disc at its periphery and alternately projecting upwardly and downwardly therefrom, each of said vanes having at least one hole extending therethrough for relieving the vortex which tends to be formed in said mixture due to rotation of said impeller therein, each of said holes having its wall tapering inwardly toward the radially outer surface of the respective vane and defining a sharp edge therewith thereby to shear solid particles in said mixture, the leading edge of each of said vanes tapering outwardly and rearwardly and having" a generally semi-circular cut-out portion formed therein with its wall tapering inwardly toward the outer surface of the vane and defining a sharp edge therewith thereby forming a sharp hook-shaped portion for shearing solid particles in said mixture, each of said vanes having its leading edge coincident with a circle concentric with the center or" said disc and defining an outwardly inclined angle with respect to a cord of said circle equal in length to the length of the same.

12. The combination of claim 11 wherein each of said vanes is identical and has at least two horizontally spacedapart holes therein, wherein each of said holes at the outer surface of the respective vane has a diameter approximately half the height of the vane, wherein the ratio of the height of said vanes to the diameter of said circle is between approximately one-to-fifteen and one-to-twentyfive, wherein the taper of said leading edge of said vanes is between approximately 20 and approximately 40 from the vertical, and wherein said angle defined by each of said vanes is between approximately 10 and approximately 30 References Cited in the file (-1 this patent UNITED STATES PATENTS 

